Factors affecting actions of Neuromuscular blockers

Several factors influence the action of neuromuscular blockers, these include:

1.      Blood flow to muscles

If blood flow is rapid, onset of action is rapid and duration of action is short.

2. Temperature

Hyperthermia potentiates the effects of non-depolarizing neuromuscular blockers, while hypothermia potentiates the effects of depolarizing neuromuscular blockers.

3. pH

Acidosis potentiates the effects of non-depolarizing neuromuscular blockers.

4. Potassium concentration

Hyperkalemia potentiates the effects of depolarizing neuromuscular blockers. Hypokalemia potentiates the effects of non-depolarizing neuromuscular blockers.

5. Antibiotics

Antibiotics like amino glycosides, streptomycin, decrease the release of acetylcholine at nerve terminals and thus potentiate the effects of non-depolarizing neuromuscular blockers.

6. Atypical Pseudo cholinesterase

Suxamethonium is metabolized by pseudo cholinesterase. If there is deficiency or presence of atypical pseudo cholinesterase, it might lead to respiratory paralysis or apnea.

7. Anti-arrhythmic drugs

Drugs like quinidine have curare like actions causing relaxation of muscles. They potentiate the effects of non-depolarizing neuromuscular blockers.

8. Myasthenia gravis

In myasthenia gravis, peripherally acting neuromuscular blockers are not administered.

9. Renal/ liver diseases

Care must be taken as Rapacuronium and Vecuronium are metabolized by the liver.

d-Tubocurarine and Metocurium are eliminated through the kidneys.

10. Calcium channel blockers

Calcium channel blockers potentiate the effects of depolarizing neuromuscular blockers and non-depolarizing neuromuscular blockers.

11. Diuretics

Thiazide diuretics produce hypokalemia, which potentiates the effects of non-depolarizing neuromuscular blockers.

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Skeletal Muscle Relaxants

Tubocurarine -Non-depolarizing Neuromuscular Blocker

Atracurium, Cisatracurium, Gallamine and Steroid Derivatives -Non Depolarizing Neuromuscular Blockers

Suxamethonium -Depolarizing Neuromuscular Blocker

Benzodiazepines as Centrally Acting Skeletal Muscle Relaxants

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Mephenesin and Meprobamate -Propandiol Derivatives

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